Patent GB-776013-A (GB)
Title: Improvements in and relating to door locks, for example for undercarriage doors
Inventor: SWALES FRANK
IPC: B64C25/26
Filed: 1954-11-26
Abstract: 776,013. Door latches. ENGLISH ELECTRIC CO., Ltd. Nov. 25, 1955 [Nov. 26, 1954], No. 34422/54. Class 44. In a door lock for aircraft, a roller or rollers are pivoted on the aircraft door and a hook. shaped latch or latches each having an inner cam face are pivoted on the aircraft structure or vice versa, said latch or each latch when swung in the closing direction engaging its associated roller and drawing the door in the closing direction thereof so as to ensure positively the completion of its closing movement. In the construction shown in Fig. 3, a link 18 is pivotally connected to the latch 6 and this link is connected to a second link 20 which is pivotally connected to a pair of plates 14, between which the latch is mounted. The two links 18 and 20 form a toggle mechanism which when its three pivot pins 17, 19 and 21 are aligned holds the latch 6 in its disengaged position. The door is opened and closed by means of a jack and during the closing movement of the door a striker pin on the door engages a plate 201 pivoted to the link 20 and breaks the toggle so that the latch can move into engagement with the roller under the pressure of a jack 16. The door is opened by actuating the jack 16 to pull the latch 6 from its roller 4 and once the latch 6 is clear of the roller the door jack can operate to open the door. Movement of the toggle links 18, 20 to their aligned position is assisted by a spring-loaded telescopic link 25 which is pivoted to the link 20 and also pivoted on the plates 14. Independently pivoted on the pin 21 is a feeler 22 which is positioned by adjustable screw stops 23, 24. If on opening the door the striker pin 5 does not completely clear the feeler 22 it imparts a clockwise jerk to it which moves the toggle mechanism to its aligned position and hence moves the latch 6 out of the way of the roller on the door. The latch 6 can be connected by linkage indicated at 9 to auxiliary latches of similar shape which also engage rollers on the door, these auxiliary latches being operated simultaneously with the latch 6. A microswitch can be associated with one of the latches so that when the latch is moved to its engaged position the microswitch operates to indicate to the pilot that the door has been closed. In a modification, Fig. 5, a single jack 203 is used both for moving the door and also for moving the latch 206. The jack 203 has one end pivotally connected to the door 201 and its other end is pivotally connected to one arm of a two-armed lever 210. The other arm of the two-armed lever 210 is connected by a rod 209 to an arm 215 of the latch 206. Hence when the jack 203 is extended it first turns the latch 206 about its pivot 213 to disengage it from a roller 204 on the door and on further expansion swings the door open. When the jack is retracted to close the door a striker pin 205 breaks a toggle mechanism formed by links 218, 220 which holds the latch in its open position and hence allows the jack to engage the latch with the roller 204 to fasten the door. In a modification of the second embodiment the latch and toggle mechanism can be pivoted on the door and the roller carried by the door frame.